1. Field of the Invention
The invention relates generally to magnetic storage devices and systems, and more particularly to methods and systems for overwrite protected or archive magnetic storage devices such as storage tape cartridges.
2. Description of the Related Art
Magnetic storage devices remain a viable solution for the storage and retrieval of large amounts of data. The use of half-inch magnetic tape cartridges, e.g., such as digital linear tape (“DLT”) or linear tape open (“LTO”) formats, is well known in the art. Generally, a magnetic storage tape is streamed by a magnetic data transducer head and data is recorded along multiple closely spaced tracks on the tape. The tape may be similarly streamed by the transducer head to read back the stored data. Magnetic storage devices are generally read/write capable and may be erased and written over many times during their lifetime.
In some instances users desire to store data in a non rewritable manner, e.g., such that the data is recorded to the storage device and further writing to the storage device is prevented. This format is typically referred to as a Write Once Read Many (or “WORM”) format. Typically, WORM formatted storage devices allow a single write operation and are thereafter a read-only storage device. For example, after data is written to the storage medium of the device, the data cannot be erased, modified, or overwritten by the drive. Optical storage devices such as compact discs are more frequently utilized as WORM media because they generally store information in a permanent form by creating non-removable pits in the media surface.
WORM storage devices are often desirable for protection against accidental or intentional modifications of the data. In other cases, WORM storage devices may be used to satisfy certain regulatory agencies, e.g., relating to financial or medical data storage uses. Accordingly, WORM storage devices are often referred to as “archival” storage devices, where the intent is that the stored data remain secure and unaltered.
Traditionally, data preservation problems have been addressed by providing physical switches, locks, slides, or the like that prevent a drive from recording to a storage medium after the switch has been moved to a WORM mode. For example, a drive may record information to the storage device with the switch in a first position allowing the drive to write to the storage device. Moving the switch to a second write protected position makes the storage device “read-only,” e.g., where a suitable drive recognizes the write protected position and is prevented from writing to the storage device. Standard magnetic tape cartridges, such as DLT cartridges, include a record switch that when in a proper position prevents a DLT drive from writing to the storage tape and thereby allows a DLT tape to become read only. The record slide switch, however, may be intentionally or inadvertently reversed to make the media writeable once again. Once the storage device is writeable, data stored thereon can be easily lost or altered if the system overwrites new data over the previously stored data.
In other examples, a record switch is more permanent, for example, a tab that breaks away to make the device read only or a record slide that permanently locks in place. Such permanent “read only” solutions, however, have several drawbacks related to magnetic storage cartridge devices. Once a storage cartridge is dedicated as read only, additional data can not be recorded to any remaining storage capacity of the tape. Accordingly, tape utilization is generally inefficient, especially with the massive storage capacities of typical storage cartridges. For example, files that are desirably stored on a WORM device are often much smaller than the capacity of the WORM device resulting in large amounts of unused and inaccessible storage capacity. The lost storage capacity increases the number of storage devices and cost for storing a given amount of data in a protected manner. Additionally, the increase in storage devices for a given amount of data may slow data access time because the data is stored on a greater number of storage devices, requiring more load/unload operations.
Additionally, archive storage functions are often satisfied with special cartridges (distinct from standard read/write cartridges) and compatible tape drives. For example, a cartridge may include certain characteristics such as size, surface features, cartridge leader features, data format, and the like to be recognized by the drive as a WORM device. Such systems are generally undesirable because of the additional cost of using separate cartridges and/or drives to perform write protected or archival functions.
Accordingly, methods and systems for converting an otherwise standard rewriteable magnetic storage device into an archive or write protected type storage device, and further allowing write append functions while protecting previously stored information, are desired.